Defoaming Compositions

ABSTRACT

Cement compositions and processes for reducing air entrainment in a cement composition generally include mixing a hydraulic cement with a defoamer compositions including one or more organic acid ester polymers selected from an organic acid ester of polyethylene oxide polymer, an organic acid ester of polypropylene oxide polymer, and a mixture thereof. The compositions may further comprise an organic acid ester of an ethylene oxide-propylene oxide block copolymer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application61/541,790, filed Sep. 30, 2011, which is incorporated herein byreference in its entirety.

FIELD OF THE ART

The present disclosure generally relates to defoaming compositions andmethods for reducing air entrainment in fluids.

BACKGROUND

Worldwide, it is estimated that 1.8 billion tonnes of Portland cementare produced annually making it one of the most widely used manmadeproducts on earth. Concrete and other cement-based materials define amajor component of the materials used in civil engineering applicationssuch as buildings, bridges, roads and other transportationinfrastructures, as well as underground constructions such as cementinga well bore.

Primary cementing is the process of placing cement in the annulusbetween the casing and the formations exposed to the wellbore. Since itsinception in 1903, the major objective of primary cementing has alwaysbeen to provide zonal isolation in the oil, gas and water wells. Toachieve this objective, a hydraulic seal must be created between thecasing and cement and between the cement and the formations, while atthe same time preventing fluid channels in the cement sheath. Oil andgas cementing service companies have introduced various chemicaladditives in order to achieve and improve desired properties of cementslurries. Many of such cement additives can cause the slurry to foamduring mixing. Excessive slurry foaming can have several undesirableconsequences. Slurry gelation can result, and loss of hydraulic pressureduring pumping can occur owing to cavitation on the mixing system. Inaddition, air entrainment may cause undesired slurry densities to bepumped down hole as measured density at surface will be different thanactual downhole density increasing the risk of formation damage.

During slurry mixing, a densitometer or mass flow meter is used to helpfield operators proportion the solid and liquid ingredients. If air ispresent in the slurry at the surface, the density of the system“cement+water+air” is measured by the densitometer. Since the airbecomes compressed downhole, the true downhole slurry density becomeshigher than the measured surface density which can damage the formation.Antifoaming or defoaming agents are usually added to the mix water ordry-blended with the cement to prevent such problems. They may also beused for breaking foamed fluids. In such applications, defoamer may beutilized to break the excess foamed fluid returned to surface after welltreatment and thus facilitate disposal process. In general, desirableantifoaming or defoaming agents, have the following characteristics tobe effective: a) insoluble in the foaming system, and b) lower surfacetension than the foaming system. The antifoaming agent functions largelyby spreading on the surface of the foam or entering the foam lamella.Because the film formed by the spread of antifoam on the surface of afoaming liquid does not support foam, the foam situation is alleviated.

BRIEF SUMMARY

Disclosed herein are defoaming compositions comprising one or moreorganic acid ester polymers selected from an organic acid ester ofpolyethylene oxide polymer, an organic acid ester of polypropylene oxidepolymer, and a mixture thereof. In certain embodiments, the compositionsmay further comprise an organic acid ester of an ethyleneoxide-propylene oxide block copolymer. Cement compositions including thedefoaming composition, methods for reducing air entrainment in cementcompositions, and methods for cementing a subterranean formation arealso disclosed herein.

The disclosure may be understood more readily by reference to thefollowing detailed description of the various features of the disclosureand the examples included therein.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a graph of the defoaming effect of various dioleate esters ofpolyoxyethylene (EO) polymers on cement slurry density. Averagemolecular weight of EO DO −1, EO DO −2 and EO DO −3 esters are, 828, 928and 1128 Daltons, respectively. Dosages are given as BWOC.

FIG. 2 is a graph of the defoaming effect of various dioleate esters ofpolyoxypropylene (PO) polymers on cement slurry density. Averagemolecular weight of PO DO −1, PO DO −2 and PO DO −3 esters are, 1528,2528 and 4528 Daltons, respectively. Dosages are given as BWOC.

FIG. 3 is a graph of the defoaming effect of PO DO esters in combinationwith EO or EO/PO diesters. Defoaming compositions are described in Table4.

FIG. 4 is a graph of the defoaming effect of EO DO esters, EO/POdiesters, and various mixtures thereof. Defoaming compositions aredescribed in Table 5.

DETAILED DESCRIPTION

Defoaming compositions and methods for reducing the air entrainment in afluid such as a cement composition are provided. The defoamingcompositions generally comprise one or more organic acid ester polymersselected from an organic acid ester of polyethylene oxide polymer, anorganic acid ester of polypropylene oxide polymer, and a mixturethereof. In certain embodiments, the compositions may further comprisean organic acid ester of an ethylene oxide-propylene oxide blockcopolymer.

In other embodiments, one or more organic acid ester polymers selectedfrom (a) an organic acid ester of polyethylene oxide polymer, (b) anorganic acid ester of polypropylene oxide polymer, and (c) an organicacid ester of an ethylene oxide-propylene oxide block copolymer.

In certain embodiments, the defoaming compositions comprise two or moreorganic acid ester polymers selected from (a) an organic acid ester ofpolyethylene oxide polymer, (b) an organic acid ester of polypropyleneoxide polymer, and (c) an organic acid ester of an ethyleneoxide-propylene oxide block copolymer.

In any of the foregoing embodiments, the organic acid ester compoundshave a low acid number, for example less than 15.

These defoaming compositions provide effective foam control by reducingair entrainment relative to other conventional defoamers, are relativelybiodegradable, and are less toxic.

In one embodiment, the composition comprises an organic acid ester ofpolyethylene oxide polymer. In another embodiment, the compositioncomprises an organic acid ester of polypropylene oxide polymer. Incertain embodiments, the composition comprises an organic acid ester ofan ethylene oxide-propylene oxide block copolymer. In anotherembodiment, the composition comprises an organic acid ester of anethylene oxide-propylene oxide block copolymer and an organic acid esterof polyethylene oxide polymer or an organic acid ester of polypropyleneoxide polymer.

In one embodiment, the composition comprises an organic acid ester ofpolyethylene oxide polymer and an organic acid ester of polypropyleneoxide polymer. In one embodiment, the composition comprises an organicacid ester of polyethylene oxide polymer and an organic acid ester of anethylene oxide-propylene oxide block copolymer. In another embodiment,the composition comprises an organic acid ester of polypropylene oxidepolymer, and an organic acid ester of an ethylene oxide-propylene oxideblock copolymer.

In one embodiment, the composition comprises an organic acid ester ofpolyethylene oxide polymer of the formula:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group having from 3 to 40 carbon atoms; and n′ is 4 to23.

In one embodiment, the composition comprises an organic acid ester ofpolypropylene oxide polymer of the formula:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group having from 3 to 40 carbon atoms; and n is 16 to68.

In one embodiment, the composition comprises an organic acid ester of anethylene oxide-propylene oxide block copolymer of the formula:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group having from 3 to 40 carbon atoms, a is 2 to 8and b is 16 to 68.

In one embodiment, the defoaming composition comprises an organic acidester of polyethylene oxide polymer and an organic acid ester ofpolypropylene oxide polymer. In certain embodiments, the organic acidester moieties of the organic acid ester of polyethylene oxide polymerand the organic acid ester of polypropylene oxide polymer are the same.In certain embodiments, the organic acid ester moieties of the organicacid ester of polyethylene oxide polymer and the organic acid ester ofpolypropylene oxide polymer are the different.

In one embodiment, the defoaming composition comprises an organic acidester of polyethylene oxide polymer and an organic acid ester of anethylene oxide-propylene oxide block copolymer. In certain embodiments,the organic acid ester moieties of the organic acid ester ofpolyethylene oxide polymer and the organic acid ester of an ethyleneoxide-propylene oxide block copolymer are the same. In certainembodiments, the organic acid ester moieties of the organic acid esterof polyethylene oxide polymer and the organic acid ester of an ethyleneoxide-propylene oxide block copolymer are the different.

In one embodiment, the defoaming composition comprises an organic acidester of polypropylene oxide polymer and an organic acid ester of anethylene oxide-propylene oxide block copolymer. In certain embodiments,the organic acid ester moieties of the organic acid ester ofpolypropylene oxide polymer and the organic acid ester of an ethyleneoxide-propylene oxide block copolymer are the same. In certainembodiments, the organic acid ester moieties of the organic acid esterof polypropylene oxide polymer and the organic acid ester of an ethyleneoxide-propylene oxide block copolymer are the different.

As used herein, the terms “polymer,” “polymers,” “polymeric,” andsimilar terms are used in their ordinary sense as understood by oneskilled in the art, and thus may be used herein to refer to or describea large molecule (or group of such molecules) that contains recurringunits. Polymers may be formed in various ways, including by polymerizingmonomers and/or by chemically modifying one or more recurring units of aprecursor polymer. A polymer may be a “homopolymer” comprisingsubstantially identical recurring units form by, e.g., polymerizing aparticular monomer. A polymer may also be a “copolymer” comprising twoor more different recurring units formed by, e.g., copolymerizing two ormore different monomers, and/or by chemically modifying one or morerecurring units of a precursor polymer.

Polyoxyethylene, also known as polyethylene glycol (PEG), has lowtoxicity and is used in variety of products. Suitable polyoxyethylenepolymers for use in the present invention are terminated with hydroxylgroups and have a molecular weight from about 200 to about 1000 Daltons.In certain embodiments, the average molecular weight of the polymer isabout 200 to about 600 Daltons. In other embodiments, the averagemolecular weight of the polymer is about 300 to about 400 Daltons.

Polyoxypropylene, also known as polypropylene glycol (PPG), is lesstoxic than PEG. Suitable polyoxypropylene polymers are terminated withhydroxyl group, having a molecular weight from 1000 to 4000 Daltons.

Organic acid esters of polyoxyethylene or polyoxypropylene are suitablefor use in the defoaming compositions described herein. The organic acidester of either the polyoxyethylene polymer or the polyoxypropylenepolymer is the reaction product of the polymer and an organic acid thathas at least one carboxylic acid group, including mono-, di- ormulti-carboxylic acid functionalities. Suitable organic acids include,without limitation, oleic acid, stearic acid, suberic acid, azelaicacid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid,and mixtures thereof. The organic acid ester of the polyoxypropylenepolymer or the polyoxyethylene polymer are of the formulas shown below:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group having from 3 to 40 carbon atoms, n is 16 to 68and n′ is 4 to 23. Many PEG and PPG diesters are commercially available.

The block copolymer of ethylene oxide and propylene oxide is notintended to be limited to any particular structure and is commerciallyavailable in several types. Suitable polyoxyethylene-polyoxypropylenecopolymers are terminated with hydroxyl groups and generally have anaverage molecular weight of 1000 to 5000 Daltons, and in otherembodiments, an average molecular weight of 2000 to 4000 Daltons, and instill other embodiments, an average molecular weight of 2000 to 2750Daltons and preferably possess a melting point below 20° C. For example,Poloxamers are nonionic triblock copolymers composed of a centralhydrophobic chain of polypropylene oxide flanked by two hydrophilicchains of polyethylene oxide. A schematic representation of a Poloxamercopolymer is shown here:

The ethylene oxide and propylene oxide block copolymers are also knownby trade names Pluronic® from BASF and Mulsifan from Zschimmer & SchwarzGmbH & Co. Because the lengths of the polymer blocks can be customized,many different EO/PO block copolymers exist having slightly differentproperties.

The organic acid ester of the ethylene oxide-propylene oxide blockcopolymer is the reaction product of the block copolymer and an organicacid that has at least one carboxylic acid group, including mono-, di-or multi-carboxylic acid functionalities. Suitable organic acidsinclude, without limitation, oleic acid, stearic acid, suberic acid,azelaic acid, sebacic acid, phthalic acid, isophthalic acid,terephthalic acid, and mixtures thereof.

The organic acid ester of the ethylene oxide-propylene oxide is of thegeneral structure:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group or aryl or aryl carboxylate group having from 3to 40 carbon atoms, a is 2 to 8 and b is 16 to 68. As noted above, thecomposition has a low acid value. In one embodiment, the acid value isless than 15, and in other embodiments, the acid value is less than 5.As used herein, the term acid value generally refers to the number ofmilligrams of potassium hydroxide needed to neutralize the carboxylicacid groups in one gram of polymer. Thus, in the case of di- andmulti-carboxylic acid esters, the free carboxylic acid groups, ifpresent, may be further esterified to prevent adverse effects on otherfluid properties. The particular block structure is not intended to belimited and may have an ordered (EO-PO-EO or PO-EO-PO) or randomarrangements. For example, in some embodiments, thepolyoxyethylene-polyoxypropylene portion has a polyoxypropylene backbonewith polyoxyethylene end cap whereas in other embodiments, thepolyoxyethylene-polyoxypropylene fatty acid esters have apolyoxyethylene backbone with polyoxypropylene end caps. Still further,in some embodiments, the backbone alkyl group R may further includehydroxyl containing substituents such as may occur using castor oilderivatives as the di- or multicarboxylic acid.

The polyoxyethylene-polyoxypropylene organic acid esters can be preparedby conventional means such as by a condensation reaction of the desiredalcohol (e.g., polyethylene glycol-polypropylene glycol (EO/PO) blockpolymer) with a mono-, di- or multi-carboxylic acid in the presence of asuitable catalyst at an elevated temperature. Alternatively, thepolyoxyethylene-polyoxypropylene organic acid esters can be prepared bytransesterification of the EO/PO block copolymer with a triglyceride ofthe desired mono-, di-, or multi-carboxylic acid and a base such apotassium hydroxide or other suitable alkalis as the catalyst.

In any of the foregoing embodiments, the organic acid ester may be anoleic acid ester.

In a particular embodiment, the compositions may further comprisehydrophobic solids. The optional hydrophobic solids such as silicondioxide (silica) may be used to enhance the performance of the estersdefoaming ability. The hydrophobic silica may fumed, precipitated, or amixture thereof. Other suitable hydrophobic solids include talc, clays,aluminosilcates, mica, alumina and such.

The defoaming compositions may also be diluted in a diluent system, forexample an organic diluent or mixture of diluents. Such diluents includebut are not limited to mineral oil, vegetable oil, alpha olefins,glycols, alcohols, kerosene and mixtures thereof. The defoamingcompositions may also comprise water. In particular embodiments, thedefoaming composition comprises vegetable oil.

In one embodiment, the defoaming composition comprises one or moreorganic acid ester polymers selected from (a) an organic acid ester ofpolyethylene oxide polymer, (b) an organic acid ester of polypropyleneoxide polymer, and (c) an organic acid ester of an ethyleneoxide-propylene oxide block copolymer; and each component may comprisefrom about 0 to about 100% by weight of the organic acid ester polymersin the composition. In certain embodiments, two or more types of organicacid esters polymers are included in the composition and each polymermay comprises from about 1% to about 99%, about 2% to about 98%, about5% to about 95%, about 10% to about 90%, about 15% to about 85%, about20% to about 80%, about 25% to about 75%, about 30% to about 70%, about35% to about 65%, about 40% to about 60%, about 45% to about 55%, orabout 50% each, by weight of the organic acid ester polymers in thecomposition.

The defoaming composition including the organic acid esters of thepolyoxyethylene, polyoxypropylene and/or ethylene oxide-propylene oxideblock copolymer as described herein can be added to cement compositionsat 0.01 to 1% by weight of the cement (BWOC).

The defoaming compositions can be added to the cement compositionbefore, during, or after blending of the various components of thecement composition. The defoaming compositions can be added as a liquidor as an emulsion or as dry products as may be desired for the intendedapplication. In one exemplary embodiment, the defoaming composition canbe combined with a cementitious material and a fluid such as water toform the cement composition before or during the blending of thosecomponents. This blending can occur at the pumphead, which displaces thecement composition down through the annulus of a wellbore (i.e., thearea between a pipe in the wellbore and the wall of the wellbore)wherein it is allowed to set into a hard material, for example cement.The defoaming compositions serve to prevent or reduce the formation offoam during the preparation or pumping of the cement composition or tobreak the foam from a well treatment fluid returned to the surface. Inanother embodiment, the defoaming composition can be added to an alreadyprepared cement composition before pumping the composition into asubterranean formation where it is allowed to set into a hard cement. Inthis case, the defoaming composition can serve to prevent or reduce theformation of foam in the cement composition as it is being pumped. Ineach of these embodiments, the ability of the defoaming composition toreduce the level of gas entrained in the cement composition can resultin the formation of relatively stronger cement that can properly supportthe piping in the wellbore. The defoaming composition can also beincorporated in the cement composition to help control the density ofthe ensuing hardened cement. In yet another embodiment, the defoamingcompositions can be combined with a previously foamed wellbore treatmentfluid such as a foamed cement or foamed drilling mud to break or reducethe foam therein. Due to the removal of the foam, the wellbore treatmentfluid can be readily disposed of after its use.

In one embodiment, a method for reducing air entrainment in a cementcomposition is provided, the method comprising: adding a defoamingcomposition to a cement composition wherein the defoaming compositioncomprises one or more organic acid ester polymers selected from anorganic acid ester of polyethylene oxide polymer, an organic acid esterof polypropylene oxide polymer, and mixtures thereof; wherein the airentrainment in the cement composition is reduced relative to a cementcomposition without the defoaming composition. In certain embodiments,the composition may further comprise an organic acid ester of anethylene oxide-propylene oxide block copolymer. In certain embodiments,the defoaming composition is added to the cement composition at 0.01 to1% by weight of the cement.

In one embodiment, a method for reducing air entrainment in a cementcomposition is provided, the method comprising: adding a defoamingcomposition to a cement composition wherein the defoaming compositioncomprises one or more organic acid ester polymers selected from (a) anorganic acid ester of polyethylene oxide polymer, (b) an organic acidester of polypropylene oxide polymer, and (c) an organic acid ester ofan ethylene oxide-propylene oxide block copolymer; wherein the airentrainment in the cement composition is reduced relative to a cementcomposition without the defoaming composition. In certain embodiments,the defoaming composition is added to the cement composition at 0.01 to1% by weight of the cement.

In one embodiment, a method for reducing air entrainment in a cementcomposition is provided, the method comprising: adding a defoamingcomposition to a cement composition wherein the defoaming compositioncomprises two or more organic acid ester polymers selected from (a) anorganic acid ester of polyethylene oxide polymer, (b) an organic acidester of polypropylene oxide polymer, and (c) an organic acid ester ofan ethylene oxide-propylene oxide block copolymer; wherein the airentrainment in the cement composition is reduced relative to a cementcomposition without the defoaming composition. In certain embodiments,the defoaming composition is added to the cement composition at 0.01 to1% by weight of the cement.

In one embodiment, a cement composition comprising: hydraulic cement;water; and a defoaming composition comprises one or more organic acidester polymers selected from an organic acid ester of polyethylene oxidepolymer, an organic acid ester of polypropylene oxide polymer, andmixtures thereof, is provided. In certain embodiments, the compositionmay further comprise an organic acid ester of an ethyleneoxide-propylene oxide block copolymer.

In one embodiment, a cement composition comprising: hydraulic cement;water; and a defoaming composition comprises one or more organic acidester polymers selected from (a) an organic acid ester of polyethyleneoxide polymer, (b) an organic acid ester of polypropylene oxide polymer,and (c) an organic acid ester of an ethylene oxide-propylene oxide blockcopolymer; is provided.

In one embodiment, a cement composition comprising: hydraulic cement;water; and a defoaming composition comprises two or more organic acidester polymers selected from (a) an organic acid ester of polyethyleneoxide polymer, (b) an organic acid ester of polypropylene oxide polymer,and (c) an organic acid ester of an ethylene oxide-propylene oxide blockcopolymer; is provided.

In a particular embodiment, the hydraulic cement comprises hydrauliccements comprising calcium, aluminum, silicon, oxygen and/or sulfur;Portland cements such as class A, B, C, G, and H cements according toAmerican Petroleum Institute (API) specification for materials andtesting for well cements; pozzolana cements; gypsum cements; phosphatecements; high alumina content cements; slag cements; cement kiln dust;silica cements; high alkalinity cements; and combinations comprising atleast one of the foregoing cements.

In another embodiment, a method of cementing a subterranean formation isprovided, the method comprising: displacing a cement composition intothe subterranean formation, the cement composition comprising hydrauliccement, water, and a defoaming composition comprises one or more organicacid ester polymers selected from an organic acid ester of polyethyleneoxide polymer, an organic acid ester of polypropylene oxide polymer, andmixtures thereof; and allowing the cement to set. In certainembodiments, the composition may further comprise an organic acid esterof an ethylene oxide-propylene oxide block copolymer.

In another embodiment, a method of cementing a subterranean formation isprovided, the method comprising: displacing a cement composition intothe subterranean formation, the cement composition comprising hydrauliccement, water, and a defoaming composition comprises one or more organicacid ester polymers selected from (a) an organic acid ester ofpolyethylene oxide polymer, (b) an organic acid ester of polypropyleneoxide polymer, and (c) an organic acid ester of an ethyleneoxide-propylene oxide block copolymer; and allowing the cement to set.

In another embodiment, a method of cementing a subterranean formation isprovided, the method comprising: displacing a cement composition intothe subterranean formation, the cement composition comprising hydrauliccement, water, and a defoaming composition comprises two or more organicacid ester polymers selected from (a) an organic acid ester ofpolyethylene oxide polymer, (b) an organic acid ester of polypropyleneoxide polymer, and (c) an organic acid ester of an ethyleneoxide-propylene oxide block copolymer; and allowing the cement to set.

In certain embodiments, the cement composition comprises pumping thecement composition into an annular space between the walls of a wellbore and casing during a primary of a remedial cementing operation. Inone embodiment, the hydraulic cement is foamed and the defoamingcomposition is added to the hydraulic cement in an amount effective tobreak the foam, thereby reducing gas entrainment in the hydrauliccement. In one embodiment, the defoaming composition is at 0.01 to 1%weight of the hydraulic cement.

The cement compositions can include the defoaming compositions describedherein, a cementitious material, and a sufficient amount of fluid torender the cement compositions pumpable. Any of a variety of cementssuitable for use in subterranean cementing operations may be used. Thecementitious material can include, for example, hydraulic cements whichset and harden by reaction with water. Examples of suitable hydrauliccements include but are not limited to hydraulic cements comprisingcalcium, aluminum, silicon, oxygen and/or sulfur; Portland cements suchas class A, B, C, G, and H cements according to American PetroleumInstitute (API) specification for materials and testing for wellcements; pozzolana cements; gypsum cements; phosphate cements; highalumina content cements; slag cements; cement kiln dust; silica cements;high alkalinity cements; and combinations comprising at least one of theforegoing cements. Examples of suitable fluids for use in the cementcompositions include, but are not limited to, fresh water, producedwater, seawater, brine solutions, and combinations comprising at leastone of the foregoing.

As deemed appropriate by one skilled in the art, additional additivescan be added to the cement composition for improving or changing theproperties of the cement. Examples of such additives include but are notlimited to set retarders, fluid loss control additives, dispersingagents, set accelerators, and formation conditioning agents. Otheradditives such as bentonite and silica fume can be introduced to thecement composition to prevent cement particles from settling to thebottom of the fluid. Further, a salt such as sodium chloride orpotassium chloride can be added to the cement composition.

The defoaming compositions described herein can be included in variousflowable end use materials to reduce the amount of entrained gas presentin such materials. In addition to cement compositions, other examples ofsuch end use materials include but are not limited to variouswater-based wellbore treatment fluids such as drilling muds, stimulationfluids, waste treatment compositions, water treatment compositions,leaching compositions (e.g. for mining), concrete and constructionsmaterials applications, and oil and/or gas separation compositions. Thevarious components of such compositions would be apparent to persons ofordinary skill in the art.

The following examples are presented for illustrative purposes only, andare not intended to be limiting.

EXAMPLES

For the following examples, the polymers are labeled as listed below.

Polymer type; average molecular weight Label in parentheses EO/PO DO anoleic acid ester of a polyoxyethylene- polyoxypropylene block copolymer(2528 Daltons) EO DO¹ an oleic acid ester of polyoxyethylene polymer(828 Daltons) EO DO² an oleic acid ester of polyoxyethylene polymer (928Daltons) EO DO³ an oleic acid ester of polyoxyethylene polymer (1128Daltons) PO DO¹ a dioleic ester of polyoxypropylene polymer (1528Daltons.) PO DO² a dioleic ester of polyoxypropylene polymer (2528Daltons.) PO DO³ a dioleic ester of polyoxypropylene polymer (4528Daltons.)

Example 1

In this example the compressive strength was measured for cementcompositions with a defoaming agent. Tributylphosphate is a commoncement defoamer and used as a reference to compare the performance ofdefoaming compositions. The defoaming agents are described in Table 1.Compressive strength data up to 48 hours for API class A cement with adensity of 1800 kg/m³ are shown given in Table 2. Compressive strengthtesting was carried out on CTE Model 2000-5 Ultrasonic Cement Analyzeraccording to API RP 10B-2 (Recommended Practice for Testing WellCements) operating at 4000 psi pressure and temperature of 50° C. Theresults show that defoamer containing cements meet the necessaryrequirements for compressive strength and that the defoamer compositionscan be used to create viable and useful cement blends. Minimumrequirement in well cementing is a compressive strength of 3.5 MPa after48 hours.

TABLE 1 Defoaming compositions used in compressive strength developmentstudy Label Defoaming Components Defoamer A Tributylphosphate (100%)Defoamer B EO DO² (30%) in Vegetable Oil Defoamer C EO/PO DO (30%) inVegetable Oil Defoamer D EO/PO DO (10%) + EO DO² (20%) in Vegetable Oil

TABLE 2 Compressive strength development of API Class A Cement slurrieswith 0.2% BWOC* defoamer Compressive Strength (MPa) Cement Sample 6 hrs12 hrs 18 hrs 24 hrs 36 hrs 48 hrs With Defoamer A 5.46 8.59 10.51 11.8413.24 14.12 With Defoamer B 5.98 9.19 11.11 12.58 14.45 15.23 WithDefoamer C 6.10 9.37 11.25 12.71 14.46 15.57 With Defoamer D 5.29 8.4810.26 11.63 13.16 14.01 *BWOC = By Weight Of Cement

Example 2

In this example, the effect of defoamer composition on the rheology ofAPI class A cement blends with density of 1800 kg/m³ was studied using aFann 35A viscometer at 25 and 50° C. The slurry was prepared by mixingdry cement and tap water on a Waring blender according to API RP 10B-2and allowed to condition for 20 minutes using a Chandler Engineeringmodel 1200 Atmospheric Consistometer at the given temperature. Therheology data is given in Table 3. It has been found that the defoamercomposition had minimal or no effect on the rheological behavior ofcement slurries.

TABLE 3 Rheological behavior of API Class A cement blend with density of1800 kg/m³. Shear Rate (rpm) Defoamer Temperature 600 300 200 100 6 30.2 wt % BWOC ° C. Dial Reading None 25 56.0 41.0 34.5 26.0 13.0 8.5 PODO³ 25 57.0 42.5 36.0 27.5 13.5 9.5 PO DO² 25 53.0 39.5 33.0 26.0 12.59.0 PO DO¹ 25 57.0 40.0 33.5 25.5 13.0 9.0 None 50 109.0 85.5 76.5 65.522.0 14.0 EO DO² 50 84.0 70.5 66.0 55.0 17.5 10.5 PO DO³ 50 126.0 114.094.5 79.5 21.5 14.5 EO/PO DO 50 106.0 83.0 71.0 61.0 22.0 14.0 EO/PO DO(10%) + 50 113.0 86.5 73.0 59.5 21.0 14.0 EO DO² (20%) in Veg. Oil

Example 3

In this example, defoaming characteristics of various diesters ofpolyoxyethylene (EO) compositions on API class cement A slurries withdesign density of 1650 kg/m³ containing 1% by weight of cement (BWOC) ofsodium lignosulfonate and 20% by weight of water sodium chloride wereexamined. The diesters were formed using oleic acid (designated usingDO). Lignosulfonates are commonly used in formulating cement slurries ascement dispersing agents. Densities were measured immediately after theslurry was prepared (based on API RP 10B-2 procedure) using a graduatedcylinder and weight of the slurry. Data are graphically represented inFIG. 1. All defoaming compositions tested were found to be effective onreducing air entrainment when added at 0.01% to 0.10% BWOC.

Example 4

In this example, defoaming characteristics of various diesters ofpolyoxypropylene (PO) compositions on API class cement A slurries withdesign density of 1650 kg/m³ containing 1% BWOC of sodium lignosulfonateand 20% by weight of water sodium chloride were examined. The diesterswere formed using oleic acid. Lignosulfonates are commonly used informulating cement slurries and is generally known as cement dispersingagents. Densities were measured immediately after the slurry wasprepared (based on API RP 10B-2 procedure) using a graduated cylinderand weight of the slurry. Data are graphically represented in FIG. 2.All defoaming compositions tested were found to be effective on reducingair entrainment when added at 0.05% to 0.20% BWOC.

Example 5

Many cement additives can cause the slurry to foam during mixingincluding surface active agents such as dispersants. In this example,performance of various defoaming compositions were examined in a highlyfoaming system containing sodium lignosulfonate (1% BWOC), sodiumchloride (20% by weight of water) and API class A cement with a designeddensity of 1650 kg/m³. Data are graphically represented in FIG. 3 anddefoaming compositions are described in Table 4. As shown in FIG. 3, inthe absence of defoamer, air entrainment causes the slurry density (1039kg/m³) to be significantly lower than the designed density of 1650kg/m³. In contrast, all defoamer compositions (added at 0.10% BWOC) wereeffective in antifoaming/defoaming in such a system.

TABLE 4 Description of defoaming compositions used in Example 5.Composition # Defoaming Chemistry Diluent 1 10% EO/PO DO & 30% PO DO³Vegetable Oil 2 20% EO/PO DO & 20% PO DO³ Vegetable Oil 3 30% EO/PO DO &10% PO DO³ Vegetable Oil 4 10% EO DO² & 30% PO DO³ Vegetable Oil 5 20%EO DO² & 20% PO DO³ Vegetable Oil 6 30% EO DO² & 10% PO DO³ VegetableOil

Example 6

In this example, the effect of the addition of 0.1% of defoamingcomposition by weight of cement (BWOC) on a cement compositioncontaining 1% BWOC sodium lignosulfonate and 20% by weight of watersodium chloride was examined. Slurry density was measured immediatelyafter mixing the dry cement with brine water and the dispersant. Dataare graphically represented in FIG. 4 and defoaming compositions aredescribed in Table 5. As shown in FIG. 4, formulations containing bothdiesters of EO polymers and diesters of EO/PO copolymers were found tobe effective defoaming agents based on proximity of measured density anddesign density data.

TABLE 5 Description of defoaming compositions used in Example 6.Composition # Defoaming Chemistry Diluent 1 20% EO/PO DO Vegetable Oil 220% EO DO² Vegetable Oil 3 20% EO/PO DO & 20% EO DO² Vegetable Oil 4 30%EO/PO DO & 10% EO DO² Vegetable Oil 5 10% EO/PO DO & 20% EO DO²Vegetable Oil 6 20% EO/PO DO & 10% EO DO² Vegetable Oil

What is claimed is:
 1. A defoaming composition comprising one or moreorganic acid ester polymers selected from an organic acid ester ofpolyethylene oxide polymer, an organic acid ester of polypropylene oxidepolymer, and a mixture thereof.
 2. The composition of claim 1, furthercomprising an organic acid ester of an ethylene oxide propylene oxideblock copolymer.
 3. The composition of claim 1, wherein the compositioncomprises an organic acid ester of polyethylene oxide polymer and anorganic acid ester of polypropylene oxide polymer.
 4. The composition ofclaim 2, wherein the composition comprises an organic acid ester ofpolyethylene oxide polymer and an organic acid ester of an ethyleneoxide-propylene oxide block copolymer.
 5. The composition of claim 2,wherein the composition comprises an organic acid ester of polypropyleneoxide polymer, and an organic acid ester of an ethylene oxide-propyleneoxide block copolymer.
 6. The composition of claim 1, wherein theorganic acid ester of polyethylene oxide polymer is of the formula:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group having from 3 to 40 carbon atoms; and n′ is 4 to23.
 7. The composition of claim 1, wherein the organic acid ester ofpolypropylene oxide polymer is of the formula:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group having from 3 to 40 carbon atoms; and n is 16 to68.
 8. The composition of claim 2, wherein the organic acid ester of anethylene oxide-propylene oxide block copolymer is of the formula:

wherein R is a linear or branched, saturated or unsaturated, alkyl oralkyl carboxylate group having from 3 to 40 carbon atoms, a is 2 to 8and b is 16 to
 68. 9. The composition of claim 1, wherein thecomposition further comprises a diluent system.
 10. The composition ofclaim 9, wherein the diluent system comprises an organic diluent. 11.The composition of claim 1, wherein the organic acid ester is thereaction product of the polymer and an organic acid having at least onecarboxylic acid group.
 12. The composition of claim 11, wherein theorganic acid is oleic acid, stearic acid, suberic acid, azelaic acid,sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, or amixture thereof.
 13. The composition of claim 1, further comprising ahydrophobic solid.
 14. A method for reducing air entrainment in a cementcomposition, the method comprising: adding a defoaming composition to acement composition wherein the defoaming composition comprises one ormore organic acid ester polymers selected from an organic acid ester ofpolyethylene oxide polymer, an organic acid ester of polypropylene oxidepolymer, and a mixture thereof; wherein the air entrainment in thecement composition is reduced relative to a cement composition withoutthe defoaming composition.
 15. The method of claim 14, wherein thedefoaming composition further comprises an organic acid ester of anethylene oxide propylene oxide block copolymer
 16. The method of claim14, wherein the defoaming composition is added to the cement compositionat 0.01 to 1% by weight of the cement.
 17. A cement compositioncomprising: hydraulic cement; water; and a defoaming compositioncomprises one or more organic acid ester polymers selected from anorganic acid ester of polyethylene oxide polymer, an organic acid esterof polypropylene oxide polymer, and a mixture thereof.
 18. The cementcomposition of claim 17, wherein the defoaming composition furthercomprises an organic acid ester of an ethylene oxide propylene oxideblock copolymer.
 19. The cement composition of claim 17, wherein thehydraulic cement comprises hydraulic cements comprising calcium,aluminum, silicon, oxygen and/or sulfur; Portland cements such as classA, B, C, G, and H cements according to American Petroleum Institute(API) specification for materials and testing for well cements;pozzolana cements; gypsum cements; phosphate cements; high aluminacontent cements; slag cements; cement kiln dust; silica cements; highalkalinity cements; and combinations comprising at least one of theforegoing cements.
 20. A method of cementing a subterranean formation,the method comprising: displacing a cement composition into thesubterranean formation, the cement composition comprising hydrauliccement, water, and a defoaming composition comprises one or more organicacid ester polymers selected from an organic acid ester of polyethyleneoxide polymer, an organic acid ester of polypropylene oxide polymer, anda mixture thereof; and allowing the cement to set.
 21. The method ofclaim 20, wherein the defoaming composition further comprises an organicacid ester of an ethylene oxide propylene oxide block copolymer.
 22. Themethod of claim 20, wherein displacing the cement composition comprisespumping the cement composition into an annular space between the wallsof a well bore and casing during a primary of a remedial cementingoperation.
 23. The method of claim 20, wherein the hydraulic cement isfoamed and the defoaming composition is added to the hydraulic cement inan amount effective to break the foam, thereby reducing gas entrainmentin the hydraulic cement.
 24. The method of claim 20, wherein thedefoaming composition is at 0.01 to 1% weight of the hydraulic cement.